#!/usr/bin/env node

const { Readable } = require('stream');

let c = 'a'.charCodeAt(0);

class MyReadable extends Readable {
    constructor() {
        super();
    }

    _read() {
        this.push(String.fromCharCode(c++));
        if (c > 'z'.charCodeAt(0)) {
            this.push(null);
        }
    }
}

let rs = new MyReadable();
rs.pipe(process.stdout);